302 Surgical Treatment
meniscal pathology. The theoretical mechanism
and clinical goal seem to be realized in general.
However, the biomechanical and biological con-
sequences are significant and the procedure is
not always effective in accomplishing its objec-
tive. Therefore, the pros and cons of meniscal
release should be carefully weighed in deter-
mining indications and communicating options
and prognoses to clients.
Effect of meniscal release on joint
biomechanics and biology
Medial meniscal release involves a complete
radial transection of the tissue. Several stud-
ies have investigated the effects of release on
meniscal function to determine if this procedure
has detrimental effects on the joint (Pozziet al.
2006; Pozziet al.2008; Lutheret al.2009; Pozzi
et al.2010). The complex material properties
and functional anatomy of the meniscus allows
it to absorb energy by undergoing constrained
elongation, as a load is applied through the sti-
fle (see Chapter 4). As the joint compresses, the
wedge-shaped meniscus will normally slightly
extrude peripherally as its circumferentially
oriented collagen fibers elongate. Extrusion and
elongation are limited by the large tensile hoop
stress developed within the strong circumfer-
ential collagen fibers bundles of the menisci
and their cranial and caudal attachments to
tibial bone. This hoop stress is critical to normal
meniscal functions and joint health. Meniscal
release eliminates the ability of the meniscus
to develop necessary hoop tension. Similar to
a hammock that has lost its anchor points, a
released meniscus ‘collapses’ and undergoes
unconstrained extrusion under weight-bearing
because of the lack of continuous circumferen-
tial fibers with cranial and caudal attachments
(see also Chapter 4; Figure 4.4). The radial
transection renders the meniscus functionally
equivalent to a hemi- or a complete meniscec-
tomy (Pozziet al.2008).Ex vivostudies have
shown that radial transections at various loca-
tions redistribute and concentrate the weight-
bearing load to a small area in the caudal aspect
of the femoro-tibial articulation (Figure 36.1)
(Pozziet al.2008; Pozziet al.2010). As expected,
complete radial transection, release, at any
(B)(A)Figure 36.1 Illustration of contact pressures obtained
from the Tekscan software in the tibial plateau leveling
osteotomy-treated cranial cruciate ligament-deficient
stifle with an intact meniscus (A) and after transection of
the caudal menisco-tibial ligament (B). The caudal
meniscal release resulted in a reduced area and increased
pressure; the load across the medial compartment shifted
completely to the caudal half of the compartment. The
caudal meniscotibial ligament release and the mid-body
release are equivalent because they eliminate the hoop
tension and the ability of the meniscus to control the
radially directed force developing from axial
compression. Source: Pozziet al.2009. Reproduced with
permission from John Wiley & Sons, Inc.point in the meniscus causes a 50% decrease in
contact area and a 40% increase in magnitude of
articular surface stress in the medial compart-
ment of CrCL-deficient stifles treated with a
TPLO (Pozziet al.2010). The contribution of the
meniscus to joint stability is also crucial (Pozzi
et al.2006). By effectively deepening the tibial
contact surface, the meniscus improves joint
congruity and acts as a secondary stabilizer.
This role of the intact meniscus is especially